1. Field of the Invention
The present invention relates to a vibration sensor comprising a fixed electrode, and a diaphragm electrode having a weight member attached to a membrane surface facing away from the fixed electrode and fixedly supported at peripheries thereof, the vibration sensor being capable of outputting variations of capacitance between the fixed electrode and the diaphragm electrode as vibration signals.
2. Description of Related Art
The above-noted vibration sensor is a vibration sensor of the electret condenser microphone type (ECM type) usable for a pedometer, for example. Conventionally, a weight member in the form of a thin cylindrical member or the like is attached to the diaphragm electrode in order to detect low frequency vibrations generated in time of walking and the like. Also, a relatively large gap is defined between an end portion of the plate-shaped weight member and a diaphragm ring fixedly supporting the diaphragm electrode at peripheries thereof, or between the weight member and a circuit board arranged on a back side of the weight member (see Patent Document 1 and Patent Document 2, for example).
Patent Document 1: Patent Application “Kokai” No. 59-70700
Patent Document 2: Patent Application “Kokai” No. 10-9944